Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $44.99   3.267%   $46.4598   $46.46   $46.45   $46.50  
  Purchase #2 $122.95   11.306%   $136.8507   $136.85   $136.85   $136.90  
  Purchase #3 $246.44   6.859%   $263.3433   $263.34   $263.35   $263.30  
  Purchase #4 $184.55   3.524%   $191.0535   $191.05   $191.05   $191.10  
  Purchase #5 $226.44   7.797%   $244.0955   $244.10   $244.10   $244.10  
  Purchase #6 $59.33   6.285%   $63.0589   $63.06   $63.05   $63.10  
  Purchase #7 $130.64   9.719%   $143.3369   $143.34   $143.35   $143.30  
  7 purchase totals = $1,015.34       $1,088.1986   $1,088.20   $1,088.20   $1,088.30